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Conway was a legend in the math department. Possibly because he actually lived there -- at one point he got kicked out of his house, and took the office opposit

Conway was a legend in the math department. Possibly because he actually lived there -- at one point he got kicked out of his house, and took the office opposite his as a bedroom. A few months later, an artist showed up to paint portraits of famous mathematicians around the border of the ceiling. Apart from that, the login to his computer required calculating the correct day of week of 10 dates in the last 2000 years. I believe that the record was around 10 seconds. He showed me the algorithm (which isn't actually that hard), but he had a calculating ability that was truly impressive. He also bet his salary on a series of backgammon games that were played in the common room -- he won, but just barely. Apart from that, he'd sometimes grab an undergraduate and give them a very brief tutorial on cutting edge mathematics just so he could try to explain a new theorem or paper -- he could be amazingly generous. On the other hand, he could be astoundingly mercurial -- there was a rumor that he used the stair method for grading, or that the grade was proportional to the length of the answer -- he loved math so much that he couldn't conceive of why anyone cared about their grade in his classes. Amazingly beloved by everyone who came in contact with him.

JdeBP 7y ago
It indeed isn't a particularly difficult algorithm. It's just modulo 7 arithmetic and some divisions combined with a table lookup. Martin Gardner of course covered it. I first encountered it in Shakuntala Devi's book Figuring: The Joy of Numbers, which has a slightly different lookup table. With practice, one can run it as the date is being given, a common lightning calculator trick for making things faster, and the lookup table becomes directly memorized. In practice, the algorithm is rarely applied outwith the past 400 years or even the past 100, for obvious reasons. Tweaking for the century is an afterthought in several accounts that I've read over the years.
- ColinWright 7y ago
  There are at least two algorithms. The one you outline here feels more like the one I use (and, coincidentally, Art Benjamin[0][1][2] uses), whereas Conway used one of his own devising called the Doomsday Algorithm[3]. So you're right, it's not that hard, but be aware that you may not be thinking of the algorithm Conway used. [0] https://en.wikipedia.org/wiki/Arthur_T._Benjamin https://en.wikipedia.org/wiki/Arthur_T._Benjamin [1] https://math.hmc.edu/benjamin/ https://math.hmc.edu/benjamin/ [2] https://www.ted.com/talks/arthur_benjamin_a_performance_of_mathemagic https://www.ted.com/talks/arthur_benjamin_a_performance_of_m... [3] https://en.wikipedia.org/wiki/Doomsday_rule https://en.wikipedia.org/wiki/Doomsday_rule
Mediterraneo10 7y ago
> Possibly because he actually lived there -- at one point he got kicked out of his house, and took the office opposite his as a bedroom. I get a bit envious of these stories of American academics actually being able to live in their offices. In my experience in Central Europe, you can stay overnight in your office to work, but sleeping is forbidden, even if you are the head of your department. It is not uncommon for security to patrol the offices every night to ensure that no one is using that nice sofa in their office to get some sleep.
- baxtr 7y ago
  When I did my PhD there was another PhD student of Biology who lived for 3-4 months in the lab. That was in Central Europe btw. :) He had to move out of the dorm he lived in and then didn’t want to look for something new since rents were too high for his taste. After the aforementioned months the Prof told him to find somewhere to sleep than the labs cafeteria where we used to have a couch, so he found a new place eventually.
- gbronner 7y ago
  "Living" was a bit of a misnomer. The rumor was that he'd stopped opening his mail, and thus his wife got the house in the divorce by default. The second office had a fairly long couch that he slept on, but I'd imagine he showered at the gym, and it didn't look particularly home-like. His office was always one of the more welcoming places -- he picked the one closest to the Common Room and the classrooms so he'd have more interaction with students. He also had all nature of toys, geometric models, puzzles, and games strewn around -- it was really a joy to be near him.

JdeBP 7y ago

It indeed isn't a particularly difficult algorithm. It's just modulo 7 arithmetic and some divisions combined with a table lookup. Martin Gardner of course covered it. I first encountered it in Shakuntala Devi's book Figuring: The Joy of Numbers, which has a slightly different lookup table. With practice, one can run it as the date is being given, a common lightning calculator trick for making things faster, and the lookup table becomes directly memorized. In practice, the algorithm is rarely applied outwith the past 400 years or even the past 100, for obvious reasons. Tweaking for the century is an afterthought in several accounts that I've read over the years.

ColinWright 7y ago
There are at least two algorithms. The one you outline here feels more like the one I use (and, coincidentally, Art Benjamin[0][1][2] uses), whereas Conway used one of his own devising called the Doomsday Algorithm[3]. So you're right, it's not that hard, but be aware that you may not be thinking of the algorithm Conway used. [0] https://en.wikipedia.org/wiki/Arthur_T._Benjamin https://en.wikipedia.org/wiki/Arthur_T._Benjamin [1] https://math.hmc.edu/benjamin/ https://math.hmc.edu/benjamin/ [2] https://www.ted.com/talks/arthur_benjamin_a_performance_of_mathemagic https://www.ted.com/talks/arthur_benjamin_a_performance_of_m... [3] https://en.wikipedia.org/wiki/Doomsday_rule https://en.wikipedia.org/wiki/Doomsday_rule

Mediterraneo10 7y ago

> Possibly because he actually lived there -- at one point he got kicked out of his house, and took the office opposite his as a bedroom. I get a bit envious of these stories of American academics actually being able to live in their offices. In my experience in Central Europe, you can stay overnight in your office to work, but sleeping is forbidden, even if you are the head of your department. It is not uncommon for security to patrol the offices every night to ensure that no one is using that nice sofa in their office to get some sleep.

baxtr 7y ago
When I did my PhD there was another PhD student of Biology who lived for 3-4 months in the lab. That was in Central Europe btw. :) He had to move out of the dorm he lived in and then didn’t want to look for something new since rents were too high for his taste. After the aforementioned months the Prof told him to find somewhere to sleep than the labs cafeteria where we used to have a couch, so he found a new place eventually.
gbronner 7y ago
"Living" was a bit of a misnomer. The rumor was that he'd stopped opening his mail, and thus his wife got the house in the divorce by default. The second office had a fairly long couch that he slept on, but I'd imagine he showered at the gym, and it didn't look particularly home-like. His office was always one of the more welcoming places -- he picked the one closest to the Common Room and the classrooms so he'd have more interaction with students. He also had all nature of toys, geometric models, puzzles, and games strewn around -- it was really a joy to be near him.